Solid fuel block having a self-contained wick

ABSTRACT

A solid fuel block for use as a heat source in, for example, a fruit orchard, is disclosed. The solid fuel block is composed of a single, folded container enclosing a solid hydrocarbon fuel on the bottom and four sides. The folded-in corners of the container extend into the fuel and act as a wick.

United States Patent Uhl [4 1 Jan. 25, 1972 [5 SOLID FUEL BLOCK HAVING ASELF CONTAINED WICK [72] Inventor: George A. Uhl, Markham, Ill. [73]Assignee: Atlantic Richfield Company [22] Filed: Sept. 4, 1969 21 Appl.No.: 855,279

[52] US. Cl ..43l/29l, 44/40 [51] Int. Cl ..F23d 3/16 [58] FieldofSearch ..43l/288,29l;44/40,4l,38;

[56] References Cited UNITED STATES PATENTS 3,327,505 6/1967 Brown..43l/288 3,367,758 2/1968 Ambrose et al ..44/40 3,428,410 2/1969Johnston et al.. ...l26/59.5 X 3,495,924 2/l970 Doering et a]. 1 26/595X Primary ExaminerCarroll B. Dority, Jr. Attorney-Morton, Bernard,Brown, Roberts & Sutherland and Thomas J. Clough 57] ABSTRACT A solidfuel block for use as a heat source in, for example, a fruit orchard, isdisclosed. The solid fuel block is composed of a single, foldedcontainer enclosing a solid hydrocarbon fuel on the bottom and foursides. The folded-in corners of the container extend into the fuel andact 'as a wick.

3 Claims, 2 Dratvlng Figures PATENTED JAMES I972 INVENTOR GEORGE A. UHL

BY we, MM WM ATTORNEYS SOLID FUEL BLOCK HAVING A SELF-CONTAINED WICKThis invention relates to solid fuel blocks and their use as a source ofheat for a variety of applications. More particularly, this inventionconcerns the combination of a solid hydrocarbon fuel, for instance wax,with a particular container to produce a heater especially useful forfrost or freeze protection and for other purposes.

There is a need in many parts of the country for a means for supplyingheat to citrus groves, fruit orchards, or vegetable farms to protect thecrop against damage caused by frost or freezing. Three actions that maybe taken in preventing crop damage due to frost and freezing involve theconservation of heat, mixing or stirring the air and the addition ofheat. One of the most effective ways to protect crops from cold weatheris to conserve heat by covering the area to be protected with cloth,paper, wood, glass, lathes, earth, brush, water flooding, etc. However,this procedure'has proven to be impractical, especially in protectinglarge acreages. In any case, the degree of protection is limited and thelabor cost is almost prohibitive. Irrigation and spraying with water hasalso proven to be undesirable. Although spraying crops with water doesafford some protection, if it is discontinued before the air temperaturerises above the danger point, ice may form on the trees, causingsubstantial damage. Orchard irrigation may cause temperatures to riseabout F., but this is usually insufficient to protect crops or trees.

Since the air temperature 40 feet above an orchard may be as much asabout 7 to 10 F. higher than at 5 feet above the ground, stirring theair with fans has often proved to be beneficial. These fans or windmachines usually consist of a tower equipped with a single propellerdriven by an electric motor or a gasoline or diesel engine. However,wind machines are not very effective against even a moderate, naturalair drift. Further, if conditions for heavy frost or freezing exist,there is little or no increase in air temperature with elevation and,consequently, there is no warm air to mix with the cold surface arr.

Most people who protect their crop against damages by freezing or frostdo so by adding heat through the burning of various fuels. The additionof heat in this manner is based upon the principle of temperatureinversion. On a clear, calm night there is a relatively thin layer ofcold air near the ground and a gradual increase in air temperature up toa height of 300 to 800 feet. Hot gases from the burning fuel mix rapidlywith the surrounding cold air to give a slightly increased ambient airtemperature which rises slightly and acts as a roof over the area to beheated to retain the subsequently heated air.

One of the most important single factors in crop protection by heatingis the amount of air movement near the ground. When the air is calm, aminimum number of heaters will raise the surface temperatureappreciably. Air in motion steadily carries the heat away and a greaterquantity of fuel must be consumed to obtain the same effect on surfacetemperature.

The addition of heat can be accomplished through the burning of eithersolid fuels or oil. Solid fuels include briquettes of coal or carbon,wood, oil saturated wood shavings, baled straw, automobile tires and amixture of coal dust, asphalt, sawdust, niter and the like. Many ofthese items, however, are costly and the supply limited. Also, thesefuels often give a large amount of soot and odor, and considerable laboris required for their use. Consequently, oil is a favorite fuel forfrost protection. Oil used for this purpose varies from bunker grademarine diesel fuel (about 27 API) to highly refined distillates of say3738 API. In certain parts of the country people are restricted toburning only distillate fuels in a return stack-type heater, or otherapproved stoves. Fruit growers not affected by these requirements stilluse crude oil, crankcase drainings and other inexpensive fuels. However,these cheaper fuels cause smoke which deposits an oil soot on the cropthus impairing its marketability.

Because of the expense, inadequate heating, smoke and other problemsassociated with crop heating systems, the industry has tried to developimproved means for protecting crops from frost and freezing, asillustrated by U.S. Pat. Nos. l,763,5l6; 2,435,520; 2,53 l ,82l; and3,105,484. The devices of all of these patents use a liquid fuel such asan alcohol, fuel oil such as kerosene, or any relatively inexpensive oilor other liquid material. These fuels have the inherent limitations ofbeing difficult to handle and burning very rapidly, often with a largeamount of smoke. Orchard heater smoke has little or no influence ontemperature and many, in fact, have a deleterious effect if it depositssooty residues on citrus fruits or becomes obnoxious to theneighborhood;

U.S. Pat. No. 1,763,516 disclosesa heating device formed of porousmaterial, such as limestone or fire clay, containing two separatecompartments for storing liquid fuel, one of which is filled withkerosene ora similar inflammable oil, and the other with a heavy oilsuch as a crude oil or a heavy fuel oil. In operation, kerosenepenetrates to the outside of the porous container where it burns and theheat of combustion causes the heavier liquid oil to penetrate tothe'outside of the container and burn. As can be readily seen, thisheater is very complicated in operation, produces undesirable smoke, isdifficult to extinguish once the burner has been started and isexpensive to produce and maintain.

U.S. Pat. No. 2,435,520 shows a flare composed of a porous ceramicmaterial, the central portion of which acts as a wick for the liquidfuel contained therein. As can readily be observed, the small burningsurface would have limited heating capacity and the fuel would bedissipated in a relatively short time. Also, it would appear that theheating capacity of the device would be continually decreased as thelevel of the fuel recedes, thereby reducing the surface area of the wickexposed to the liquid fuel. Both U.S. Pat. Nos. 2,531,828 and 3,105,484disclose heaters consisting of a reusable container filled with anabsorbent material impregnated with liquid fuel. The former patent usesasbestos fiber type absorbent material, whereas the latter patent usesabsorbents such as rock wool, mineral wool, glass wool, vermiculite,etc. Upon ignition, all of the fuel would burn simultaneously causing arapid use of the fuel and also making extinguishing of the fueldifficult. Thus, it is apparent that an improved heating device isneeded which is inexpensive and easy to operate and which producessufficient, essentially smokeless heat for a desired period of time.

U.S. Pat. No. 3,4l3,967 discloses a fuel block composed of a normallysolid hydrocarbon wax encased in an open top porous container made of alight weight aggregate and a binder such as sodium silicate or poitlandcement.

The heating device of the present invention is a fuel block composed ofa normally solid hydrocarbon wax encased in a container made from asingle folded sheet of a flammable, solid sheet material such ascardboard, paperboard, etc., which exhibits sufficient flexibility to befolded but has sufficient strength and rigidity to form the container.

By using the wax fuel material in a container which functions as a wickto burn the fuel contained therein, a heater is provided whichsubstantially satisfies the needs of the fruit and vegetable industry,that is, to protect crops against damage caused by frost and freezing.The wicking action of the container is essential to maintain burning ofthe fuel over an extended period of time, especially when there isappreciable air movement across the surface of the block, and mostparticularly, when the heating device is first ignited. Thus, thewaxcontainer interface at the upper surface of the wax forms a stableflame source that maintains combustioneven when a substantial wind ispresent.

In the drawings:

FIG. 1 shows an unfolded sheet of container material with the fold linesindicated thereon; and

FIG. 2 shows a solid fuel block of the invention.

As shown in FIG. I, the prefolded container is a rectangular, singlecellulosic sheet. Although the sheet is shown as a continuous, solidsheet, it can be formed from smaller pieces fitted together to form thedesired shape and size and appropriately held together, as by means ofadhesive, adhesive tape, staples or the like, to form a one-piece sheet.The sheet I is folded upwardly along the fold lines 2, 2, 2", 2", 3, 3',4, 4', 5, 5', and 6, 6', and inwardly along the fold lines 7, 8, 9 and 0to provide the container 11 as shown in FIG. 2.

The folds 2, 2, 2" and 2" define the base a of the fuel block, whilefolds 3, 3', 4, 4', 5, 5', 6 and 6 define the four side panels b, c, dand e, respectively of the fuel block. Each of the fold lines for thesides is, as shown, an extension of the fold lines defining the base. Inthis way, a rectangular container is obtained. The sheet material ineach corner lying between the sides, indicated generally as f, is foldedinwardly along the diagonal, between the corner of the base a and thecorner of sheet 1, as indicated at 7, 8, 9 and 10, respectively. Thisinward folding of the corner material provides four inwardly extendingportions 12 which when encased in the fuel block provide the heatingdevice with a self-contained wick.

The sheet 1 can be scored slightly to make folding easier. The inwardlyextending comer portions 12 can be glued together, or a retaining membersuch as a wire or strap 13 can be placed around the outside of thecontainer 11, near the bottom. Also, the folds may be stapled orotherwise attached at the center of the container. The fuel material ispreferably melted and poured into the folded container and allowed toharden, although preformed fuel blocks may be used and inserted withinthe container. v

The materials used for making the containers of the present inventionare fibrous composites such as cardboard, paperboard, or othercellulosic materials. Cardboard is particularly preferred because of itsrelatively high strength and low cost. The container can be coated onthe outside with a fire retardant material such as sodium silicate toavoid burning away the container too rapidly.

The fuels which are used in making the solid fuel blocks of the presentinvention are generally those which melt at a temperature high enough sothat they will not flow out of the container if the blocks are stored ontheir side at summer temperatures. These fuels in general are normallysolid waxes and include predominantly waxy hydrocarbon products meltingabove say about 100 F., and thus include fully refined paraffin ormicrocrystalline waxes. The fuels, although consisting substantially ofwax, may contain a minor amount, say up to about 30 percent or more byvolume, of oil. A typical fuel which is obtained from light and mediumslacks is foots oil which melts between about I l5 and l25 F. A typicalparaffin wax has a specific gravity (API) of about 34, a viscosity (SUSat 2 l0 F.) of about 53, a melting point (ASTM) of about 14 i F and apercent oil content of 22.3.

One of the features of the present invention is the relatively easyignition and extinguishing properties of the fuel block. The novelwicking action of the fuel container insures ready ignition and theflame can be extinguished by smothering and may be relit at any time.

It is also desired that the heater or fuel block give off a relativelyeven B.t.u. output as it burns down, and thus most advantageously theheater has a horizontal cross section which is essentially constant. Theheat dissipation of the fuel block of the present invention can,therefore, be substantially uniform since the fuel and air supply areessentially constant throughout the burning period for a uniform airmovement. The blocks are particularly effective in areas of the countrypreferably where there is no temperature inversion and thus no warm airroof to hold the heat near the ground. In these situations it isimportant that the heaters deliver relatively constant heat fromignition until the flame is extinguished. It is also essential that theheaters be able to withstand the climatic conditions which exist duringthat period of time when the heaters are being used, generally,throughout the frost and freezing months. The fuel blocks of the presentinvention are substantially unaffected by the extremes of temperatureconditions. In achieving the necessary B.t.u. requirements, the fueloften burns with about a 12 to 15 inch flame and with little smoke.

The solid fuel block heater of the present invention is relativelyinexpensive to produce and can be properly sized to meet the necessaryheat output required, depending upon the particular use. Frequently, theblock IS sized to expose an upper wax surface of at least about 0.15square foot, and it may be sized up to about 5 square feet withconvenience in handling being maintained; however, blocks of larger fuelcross-sectional dimensions may be made. The blocks can be stackedwithout any danger of spillage and can be stored indefinitely withoutany serious deterioration in the burning qualities of the burner. Thefuel used is not subject to spontaneous combustion, and if storagetemperatures rise above the melting point of the fuel, no difficulty isencountered except possibly spillage problems if it were necessary tomove the containers at that particular time.

In use, the heater is ignited either manually or with a chemical igniterwith the inwardly folded cornersacting as a wick to estabiish fullignition of the fuel surface. As the fuel burns, the container wallsburn away, as well as the inwardly folded corners so that very little ofthe container remains after burning out.

The usefulness of this type of heater is not restricted to orchard useand general crop use such as in vine yards, berry farms, vegetable farmsand other field crops, but also finds application in construction work,winter resort areas such as ice skating rinks and ski slopes, variousindoor applications and many other heating applications. The heaters ofthe present invention can also be used as standby equipment tosupplement existing heating facilities.

I claim:

1. A solid fuel block heater comprising a normally solid hydrocarbon waxand an ignitable container within which said wax is enclosed, saidcontainer being formed from a single solidsheet (l) of flammablematerial folded along fold lines (2, 2", 2", 2") defining the base (a)of said fuel block, said fold lines defining the base (a) as arectangular base, said sheet further being folded along fold lines (3,3', 4, 4, 5, 5', 6, 6') defining upwardly extending sides (b, c, d, e),the last said fold iines defining the sides as rectangular sides, andsaid sheet further being folded along centerlines (7, 8, 9, 10) betweenthe corners of said base (a) and corners of said sheet (I) to provideinwardly extending portions (12), said inwardly extending portions l2)defining a self-contained wick means.

2. The solid fuel block of claim 1 wherein said container is made ofcardboard.

3. The solid fuel biock of claim 2 wherein said cardboard is coated onthe outside with a fire retardant material.

UNITED STATES PATENT OFFICE CERTIFICATE CF CORRECTION Patent 3, 37,335Dated an rv 25. 372

Inventor(s) George A. Uhl

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column Line 46, reads "(2' 2", 2'', 2"'')" should read Signed and sealedthis 3rd day of October 1972.

(SEAL) Attest:

EDWARD MQFLETGHER,JR. 7 ROBERT GOTTSCHALK. Attesting OfficerCommissioner of Patents USCOMM-DC GO376-P59 U.S. GOVERNMENT PRINTINGOFFICE: I959 0"355-33 v1 PO-105O (10-69)

2. The solid fuel block of claim 1 wherein said container is made ofcardboard.
 3. The solid fuel block of claim 2 wherein said cardboard iscoated on the outside with a fire retardant material.